EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES OF POLYURETHANE POWDER COMPOSITES

In this paper, the effects of emery, lime, quartz sand and cement on the mechanical properties of polyurethane powder composites were studied by three-point flexural test, and the stress-strain curve was drawn. In the flexural test, the polyurethane cement composite formed a control group by changing the content of polyester polyol. When polyester polyol: isocyanate: cement =1:1:2, the average flexural strength of polyurethane cement was 37.1 MPa, and the strain was 10854 με.When polyester polyol: isocyanate: cement =1.15:1:2, the average flexural strength is 38.9 MPa and the strain is 23520 με.When polyester polyol: isocyanate: cement =1.3:1:2, the average flexural strength is 42.5 MPa and the strain is 32942 με. The flexural strength and ductility are improved to a certain extent due to the addition of polyester polyol.The average flexural strength of other polyurethane powder composites such as polyurethane emery test block is 45.1 MPa and the strain is 6203 με, the average flexural strength of polyurethane lime test block is 33.4 MPa and the strain is 6470 με, the average flexural strength of polyurethane quartz sand test block is 49.23 MPa and the strain is 7521 με. The results show that the flexural strength of polyurethane emery material and polyurethane quartz sand material is higher than that of polyurethane cement, which can be used to replace cement to a certain extent to reduce the cost of polyurethane composite material.

Synergistic Excitation Mechanism of CaO-SiO2-Al2O3-SO3 Quaternary Active Cementitious System

In this study, the influence of steel slag (SS) content on the strength of the cementitious materials was investigated. The quaternary active cementitious material (CaO-SiO2-Al2O3-SO3) was prepared using various proportions of steel slag (SS), granulated blast furnace slag (BFS), and desulfurized gypsum (DG). The mechanism of synergistic excitation hydration of the cementitious materials was examined using various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). The strength of the mortar test block was initially increased and decreased later with the increase of the SS content. Mortar test block with 20% steel slag, 65% granulated blast furnace slag, and 15% desulfurized gypsum with 0.35 water-binder ratio showed the highest compressive strength of 57.3 MPa on 28 days. The free calcium oxide (f-CaO) in the SS reacted with water and produced calcium hydroxide (Ca(OH)2) which created an alkaline environment. Under the alkaline environment, the alkali-activated reaction occurred with BFS. In the early stage of hydration reaction, calcium silicate hydrate (C-S-H) gel and fibrous hydration product ettringite (AFt) crystals were formed, which provided early strength to the cementitious materials. As the hydration reaction progressed, the interlocked growth of C-S-H gel and AFt crystals continued and promoted the increase of the strength of the cementitious system.

#3071 Acute escitalopram administration increases premature responding as a function of reward magnitude in healthy male volunteers

ObjectivesImpulsivity is a multifaceted construct that involves a tendency to act prematurely with little foresight, reflection or control. Waiting impulsivity is one aspect of action impulsivity and is commonly studied in animals using tasks such as the 5-choice serial reaction time task (5CSRTT).1 It is neurochemically distinct from motor response inhibition defined as the ability to restrain or cancel a pre-potent motor response and measured with no-go and stop-signal tasks respectively.1 Serotonin modulates waiting impulsivity as decreased serotonergic transmission promotes premature responding in the rodent 5CSRT and the human analogue 4CSRT task.2 Potential mechanisms contributing to waiting impulsivity include proactive or tonic inhibition, motivational processes and sensitivity to feedback and delay.3 Higher waiting impulsivity in response to high reward cues was previously associated with greater subthalamic nucleus connectivity with orbitofrontal cortex and greater subgenual cingulate connectivity with anterior insula.4MethodsWe administered a clinically relevant dose of escitalopram (20mg) in healthy subjects in a double-blind, placebo-controlled, parallel-groups design study and assessed its effect on waiting impulsivity using the well-validated 4CSRT task. Compared to previous studies,2 4 we added another test block with increased potential gain to assess the interaction between premature responding and reward processing. We recruited sixty-six healthy participants who completed an extensive neuropsychological test battery assessing probabilistic reversal learning, set-shifting, response inhibition, emotional processing and waiting impulsivity. Sixty participants (N=60, 26 females, 34 males) completed the 4CSRT task with N=30 in the escitalopram and N=30 in the placebo group, due to technical errors and experienced side-effects for the remaining six participants. The results of the other cognitive tasks are reported separately.5ResultsEscitalopram increased premature responding in the high incentive condition of the 4CSRT task, p=.028, t= 2.275, this effect being driven by male participants, p=.019, t=2.532 (for females, p>.05). We further show that escitalopram increased premature responses after a premature response in the same block again in male participants only, p=.034, Mann-Whitney U= 61.500. We found no correlation between premature responding in the 4CSRT task, in any test block, and the Stop-signal reaction time, the primary measure of the stop-signal task completed by the same participants (reported in [5]).ConclusionsWe show that acute escitalopram increased premature responding in healthy male participants only in high incentive conditions potentially mediated potentially through an effect on increased incentive salience. We also show that acute escitalopram increased perseverative responding thus producing a maladaptive response strategy. We show no correlation between SSRT and premature responding in the same participants consistent with these two forms of impulsivity being neurochemically and anatomically distinct. We interpret our findings in the context of acute escitalopram decreasing serotonergic transmission in some brain areas through inhibitory actions on terminal 5-HT release mediated by auto-receptors on raphe 5-HT neurons analogous to the presumed transient reduction in 5-HT activity caused by ATD.5Our findings provide further insights in the relationship of premature responding and reward processing and our understanding of pathological impulse control behaviours.References Eagle DM, Bari A, Robbins TW. The neuropsychopharmacology of action inhibition: cross-species translation of the stop-signal and go/no-go tasks. Psychopharmacology 2008;199(3):439456. Worbe Y, Savulich G, Voon V, Fernandez-Egea E, Robbins TW. Serotonin depletion induces waiting impulsivityon the human four-choice serial reaction time task: cross-species translational significance. Neuropsychopharmacology 2014;39(6):15191526. Voon V. Models of impulsivity with a focus on waiting impulsivity: translational potential for neuropsychiatric disorders. Current Addiction Reports 2014;1(4):281288. Mechelmans DJ, Strelchuk D, Doamayor N, Banca P, Robbins TW, Baek K, et al. Reward sensitivity and waiting impulsivity: shift towards reward valuation away from action control. International Journal of Neuropsychopharmacology 2017;20(12):971978. Skandali N, Rowe JB, Voon V, Deakin JB, Cardinal RN, Cormack F, et al. Dissociable effects of acute SSRI (escitalopram) on executive, learning and emotional functions in healthy humans. Neuropsychopharmacology 2018;43(13):26452651.

PREPRINT: Different target modalities improve the single-probe protocol of the response time-based Concealed Information Test

To detect if someone hides specific knowledge (called ‘probes’), the reaction time-based Concealed Information Test (RT-CIT) asks the examinee to classify items into two categories (targets/non-targets). Within the non-targets, slower RTs to the probes reveals recognition of concealed information. The preferred protocol examines one piece of information per test block (single probe protocol), but its validity is suboptimal. The aim of this study was to improve the validity of the single probe protocol by presenting the information in multiple modalities. In an online study (n = 388) participants were instructed to try to hide their nationality. The items referring to the nationality were presented as words, flags, and maps. Increasing the number of modalities of the targets (BF10 = 37), but not of the probes (BF01 = 6), increased the validity of the RT-CIT. This broadens range of the RT-CITs’ applicability, which is an important step towards application in practice.

Analisis Pengaruh Metode Pembersihan Core, Pengeringan Core, dan Bonding Test Block pada Uji Flatwise Sandwich Carbon Epoxy dengan Glass Core

Penggunaan komposit sebagai pengganti material logam dalam bidang rekayasa sudah semakin banyak digunakan salah satunya panel komposit dengan struktur sandwich. Core pada komposit sandwich memiliki peranan penting sebagai penopang dari skin yang digunakan. Pengujian ini bertujuan untuk mengetahui nilai kekuatan tarik flatwise dari variasi yang digunakan beserta pengaruhnya. Pengujian yang dilakukan adalah uji flatwise (ASTM C297). Hasil uji flatwise dengan nilai tertinggi ada pada variasi pembersihan menggunakan spray MEK, pengeringan menggunakan suhu ruang, dan bonding menggunakan tablepress dengan nilai rata-rata 5,67 MPa. Dari variasi yang digunakan, keseluruhannya memberikan pengaruh pada hasil pengujian.

[Technical Note] The Effect of Variables on Laboratory Termite Testing: Part II—Effect of Grain Orientation of Test Blocks

The effect of test-block grain orientation on laboratory termite tests using American Wood-Preservers' Association Standard E1-97 was evaluated using Coptotermes formosanus. This research revealed that testing of samples with the 6-mm direction in either the longitudinal or the tangential direction was appropriate. The E1 standard was subsequently modified to allow either.

Experimental study on the influence of locked-in stress on the uniaxial compressive strength and elastic modulus of rocks

The rock contains many inclusions which produce high locked-in stress under the ground stress. In order to study the influence of locked-in stress on the mechanical properties of rocks, the rock-like materials and nitrile rubber particles are used to make a test block of the rock-like model which contains inclusions. The rubber particles will expand as the test block is heated, which creates locked-in stress in the inclusions. Uniaxial compression tests of similar model blocks with different locked-in stresses and different inclusion contents were performed by using a water bath and MTS-5T uniaxial compression testing machine. The results show that the peak strength and elastic modulus decreased with the increasement of locked-in stress and inclusion content. In the meantime, the relationship among the peak strength, the elastic modulus of the test piece, the locked-in stress and the inclusion content were obtained with the help of a mathematical fitting analysis of the quantitative formula. Furthermore, the expression and value curve of the joint impact factor are calculated. This paper evaluates the importance of the locked-in stress in the mechanical properties of the rock-like material and provide a guide for other researchers to further investigate the locked-in stress in rocks.

Research on the Inspection Parameters of Ultrasonic Phased Array for the Periodic Inspection of High-Pressure Hydrogen Vessel

Steel layered high-pressure hydrogen vessel is one of different kinds of high-pressure vessel, which is invented in China and is widely equipped in hydrogen refueling stations for its good safety and storage functions. Many of these vessels are put into application these years, and it is nearly the time for these vessels to go through periodic inspection. However, there is no such a method for the periodic inspection especially on the butt weld connecting the double-layer head and the interface forging. To conquer the difficulties about the periodic inspection, a set of periodic inspection methods was first proposed in a lasted released Chinese group standard, in which the inner ultrasonic phased array is considered to be the most complicated detecting approach. To establish effective inspection parameters, simulations and experiments were conducted on the factors, including coupling, elements and aperture, focal law, scanning approaches and ultrasound field. Standard test block and contrast test block were designed and machined and tested, then a series of feasible parameters were determined. Thus, specific probe, wedge and instrument were manufactured, and the inspection on the actual vessel product was carried out. The results showed that the proposed ultrasonic method and its inspection parameters could meet the periodic inspection well. Finally, the periodic inspection methods were established and issued as a standard.

Research on the Difference of Physical Parameters of Concrete in Saline-alkali Environment

In order to better study the corrosion of concrete in saline-alkali area, the model tests of concrete and reinforced concrete with different ions and different ion concentrations were constructed. Taking the test blocks mixed with water as the control group, the resistance and polarizability of the test block during the maintenance period were measured by rock specimen tester and rock specimen test frame. The one-way variance analysis of the measured values of each test block was carried out by spss software, investigating the difference of electrical parameters of each concrete. The results show that there is significant difference in the resistance between the clear water concrete test block and the 3% sodium sulfate concrete test block at the level of significance ≤ 0.05. For reinforced concrete test blocks, the resistivity difference between water test block and 3% sodium sulfate test block and 6% sodium sulfate test block is not significant, and the resistivity difference between water test block and 15% sodium sulfate test block and 3% sodium chloride test block is significant. No matter concrete or reinforced concrete, the polarizability of test blocks mixed with water and test blocks mixed with each solution is significantly different. Therefore, the polarizability parameters can be used to distinguish whether the concrete is corroded by salt and alkali. It is feasible to use polarizability parameter to detect concrete erosion by salt and alkali.